Roller presser backstop device for sewing machines



April 25, 1939. G. w. WESSON 2,156,045 1 ROLLER PRESSER BACKSTOP DEVICEFOR SEWING MACHINES Filed Feb. 17, 1938 Q George W hsson Patented Apr.25, 1939 UNITED STATES PATENT OFFICE- ROLLER PRESSER BACKSTOP DEVICE FSEWING MACHINES George W. Wesson, Bridgeport, Conn., assignor to TheSinger Manufacturing Company, Elizabeth, N. J a corporation of NewJersey Application February 17, 1938, Serial No. 196,907

Claims.

This invention relates to improvements in devices for preventingretrograde rotation of sewing machine presser-rollers and has for itsobject to simplify and improve the efficiency of 5 back-stop devices ofthis character.

The invention consists in the presser-roller back-stop devicehereinafter described in connection with the accompanying drawing whichillustrates a preferred embodiment of the invention and in which:

Fig. 1 is an enlarged side elevation of a rollerpresser having theimproved back-stop device, as viewed from the side opposite to thesewing machine needle. Fig. 2 represents a front elevation,

partly in section, of the roller-presser. Fig. 3 illustrates, inperspective, the back-stop detents and the holder therefor in detachedrelationship. Fig. 4 illustrates a further enlarged perspective of thedetents in engagement with a fragment of the toothed presser-roller hub.

The roller-presser illustrated in the drawing is of well knownconstruction and is employed in a sewing machine having a cloth-plate Iand a vertically reciprocatory needle-bar 2 carrying a needle 3, saidroller-presser including a presserroller 4 having a knurled peripheralwork-engaging surface 5 and a cylindrical hub 6. The hub 6 has aninternal rib I providing spaced annular recesses, as 8 and 9, for twosets of bearing-balls,

as I6 and II. The bearing-balls I6 roll upon a bearing-cone I2 of apresser-roller supporting screw-stud I3 having a ball-retaining flangeI4 at one end thereof. Threaded upon the screwstud I3 is a shoulderedbearing-cone I5 for the balls I I, the screw-stud being itself threadedinto the free end of a supporting arm I6 and secured by means of a nutI1. The supporting arm I6 extends forwardly from a roller-presserbracket I8, to which it is adjustably secured by a screw The cylindricalhub 6 of the presser-roller is annularly provided with serrations 26which lengthwise extend parallel to the axis of rotation of thepresser-roller, so that said hub 6 is in effect a ratchet-wheel.Resiliently engaging the teeth 26 to prevent retrograde rotation of thepresser-roller are adjacent detents 2I and 22 comprising, in thepreferred embodiment thereof, laterally spaced prongs of a flexible FA)leaf-spring 23. The end of the leaf-spring 23 opposite to the prongedend thereof is secured by a screw 24 against a flattened face 25provided upon a lateral extension of a carrier 26, said screw 24 passingthrough an aperture 21 in the leafspring. The carrier 26 extends rigidlyfrom the supporting arm I6 and in the present case is secured to saidsupporting arm by a screw 28 having a left-handed thread, said screwpassing through an aperture 29 in one end of the carrier 26. Thedescribed securing means for the car- '5 rier, while simple, has theadvantage that the screw is tightened responsively to a retrograderotation thrust of the presser-roller 4 upon the detent-prongs 2|, 22 sothat said detent-prongs are securely held against endwise movement. 10The detent-prong 22 is preferably slightly longer than the prong 2Iwhereby the spacing of the free ends of said prongs circumferentially ofthe serrations is less than the width of one tooth, so as to minimizethe permissible extent of retrograde rotation of the presser-roller 4. Y

The presser-roller 4 is journaled in ball-bearings to provide for freerotation thereof when the work is advanced in the direction of the arrowshown in Fig. l of the drawing. However, Q

cross-seams and similar obstructions in the work tend to induceretrograde rotation of the presserroller when freely rotatable, therebyretarding the advance of the work and causing the formation of shortenedstitches and the cutting of work, 2|! such as leather, by the needle 3.

In order to retain the advantages inherent in a freely rotatablepresser-roller, the back-stop detents employed to engage the serrations26 must necessarily engage said serrations lightly, to ob- 30 viateretarding the presser-roller. In other words, the leaf-spring prongs 2I,22, must be highly flexible. Nevertheless, it is of course essential forsaid detents to effectively withstand the thrust imparted thereto byaninduced retrograde rotation of the presser-roller.

In accordance with the present invention, the requisite flexibility andthe light pressure of the detents 2|, 22 upon the serrations 26 areobtained by employing the thin leaf-spring 23. The leaf- 46 spring 23 issupported by the carrier 26 so as to be disposed substantiallytangential to the hub 6 and preferably with both detent-prongs 2I, 22slightly flexed, at all times, in the direction of movement of theprongs to climb the crests of 45 the serrations. Consequently, anyretrograde rotation thrust of the presser-roller will always tend tofurther flex the detents 2 I 22 in the direction of the constant flexthereof. However, according to the present invention, said further flex-50 ing of the detent-prongs is limited by a backingmember 36 whichunderlies said detent-prongs. The backing member 36 is preferably in theform of a lug depending from the lateral extension of the leaf-springcarrier 26, the face of said lug ll which is proximate to thedetent-prongs 2|, 22, being flush with the flat face of said carrier. Aswill be readily understood, the backing member provides thereinforcement for the thin detent-prongs necessary to prevent saidprongs from springing out of engagement with theserrations 20 under aretrograde rotation thrust of the prejsser-roller. Furthermore, whilesaid backing member 30 permits the detent-prongs to resiliently ride theserrations 20 in the normal direction of rotation of the presser-roller4, said backing member 30 serves to stiffen the detentprongs under aretrograde rotation thrust of the presser-roller, thereby effectuallylimiting retrograde rotation of the presser-roller to a minimum.

Having thus set forth the nature of the. invention, What I claim hereinis:

1. A presser-device for sewing machines, comprising a support, awork-engaging presser-roller rotatably journaled upon said support andannularly provided with serrations, a detent disposed to resilientlyengage said serrations and thereby prevent retrograde rotation of saidpresser-roller, means for supporting said detent against endwisemovement, and a backing member disposed to limit resilient;movement ofsaid detent in one direction in response to a retrograde rotation thrustof saidpresser-roller.

2, A presser-device for sewing machines, comprising a support, awork-engaging presser-roller rotatably iournaled upon said support andannularly provided with serrations, a flexible deitentdisposed toresiliently engage said serrations and thereby prevent retrograderotation of said presser-roller, said detent being flexed in onedirection, supporting means for said detent, and means disposed to limitthe flexing of said detent in said direction in response to a retrograderotation thrust of said presser-roller.

3. A presser-device for sewing machines, com-- prising a support, awork-engaging presser-roller rotatably journaled upon said support andha-ving a peripherally serrated cylindrical hub, a flexible detentsubstantially tangential to said hub and having one end thereof inresilient engagement with the hub serrations, supporting means for saiddetent spaced from 'said hub, and a backing member underlying saiddetent between the ends thereof in position to limit flexing of saiddetent in one direction.

4. A presser-device for sewing machines, comprising a support, awork-engaging presser-roller rotatably journaled upon said support andannularly provided with serrations, a pairof flexible det'ents disposedto resiliently engage said serrations, said detents being both flexed inthe same direction, means for supporting said detents, and meansdisposed to limit the flexing of both of said detents in said directionin re-- sponse to a retrograde rotation thrust of said his

